1. Field of the Invention
The present invention pertains to recording devices in general and in particular, to high-speed positioning of the read-write head of recording devices. The high-speed positioning technology of the present invention is ideal for use in spin stands of recording devices that are used to determine performance and properties of recording devices.
2. Discussion of the Background Art
Hard disk drives (HDD) are widely used in information recording media for recording large volumes of digital data, beginning with electronic computers.
HDDs generally comprise a substrate, a magnetic disk, which is a non-magnetic disk covered with magnetic thin film, a spindle motor that is anchored to the substrate and rotates the magnetic disk at high speed, a slider that has a recording element and a head, which is the reproducing element, on its surface, a head gimbal assembly (HGA) with the slider at its end, an arm with suspension that supports the HGA, and a rotary actuator that is anchored to the substrate and drives the arm. Furthermore, a single HDD has several magnetic disks and heads depending on the recording capacity of the HDD.
The working principle of the HDD is as follows: The center of a magnetic disk is held by a spindle and rotates at high speed from 4,000 to 15,000 rotations per minute. The slider is guided by an arm that is driven by a rotary actuator and moved so that the space between the outer periphery and the innermost periphery of the magnetic disk forms an arc. Moreover, when information is being recorded or reproduced, the slider that is above the magnetic disk maintains an inclined posture so that a wedge-shaped space is formed with the magnetic disk as it floats at a very small distance above the magnetic disk under the air current that is produced on the surface of the magnetic disk rotating at a high speed. Once the slider has been positioned at a predetermined position on the magnetic disk by the rotary actuator, the magnetic disk is magnetized and information is recorded by the recording element attached to the slider. Moreover, the magnetic field from the magnetic disk is detected and information is reproduced by the reproducing element attached to the same slider.
Furthermore, recording and reproduction of information is performed on the memory region that has been made by physically subdividing the magnetic disk recording surface. For instance, reading and writing are performed on an annular memory region called a track having a predetermined width that has been made along the concentric circumference of the magnetic disk.
The HDD accumulates information and therefore, each part comprising the HDD undergoes rigorous testing because there must be complete reliability during recording and reproduction of information. A head testing device that records or reproduces information on a magnetic disk for testing and evaluates the performance and properties of the head is used to test heads.
An oblique view of the conventional head testing device 10 is shown in FIG. 1. Head testing device 10 in FIG. 1 consists of reference table 11, cassette 30 that holds head 20 at the end, carriage 12 that holds cassette 30, piezo stage 13 that fine-positions carriage 12 horizontal with respect to reference table 11, head-loading mechanism (HLM) 14 that positions piezo stage 13 perpendicular with respect to reference table 11, stage 15 anchored to reference table 11 that coarse-positions HLM 14 horizontal with respect to reference table 11, and disk rotating device 50 anchored to reference table 11 that holds the center of magnetic disk 40 with rotating shaft 51 so that magnetic disk 40 is horizontal with respect to reference table 11 and magnetic disk 40 rotates around its axis using motor 52.
A summary of the effects of the above-mentioned structure is as follows: Piezo positioner 13 is coarse-positioned by stage 15 and then carriage 12 is fine-positioned by piezo stage 13. Head 20 is positioned at a predetermined position over magnetic disk 40 by these positioning operations. Furthermore, head 20 is moved up and down above magnetic disk 40 by HLM 14 and floats above the surface of magnetic disk 40 or rests above the surface of magnetic disk 40. Head 20 generates a magnetic field when it floats above the surface of magnetic disk 40 and writes information on magnetic disk 40 or detects a magnetic field and reads information from the magnetic disk.
The following are items evaluated by a head testing device. These include the track average amplitude (TAA), which is the average amplitude of reproduction signals that are output from the head; the track profile (TP) representing the TAA distribution relative to displacement from the track center line (TCL) within a track; the overwrite (OW), which is represented by the attenuation factor of the LF signals when the highest frequency signals (HF signals hereafter) are overwritten on the lowest frequency signals (LF signals hereafter) recorded on a magnetic disk; the bit error rate (BER), etc. For instance, the head moves in micro-increments from one side of the track width to the other in order to determine the TAA distribution in the direction of width with the track center line serving as the center in the track profile determinations. Moreover, it also moves between tracks because there are fluctuations, etc., in determination results between the inner and outer periphery of the magnetic disk. Thus, in addition to the magnetic disk being read by the head, the head also frequently moves during head tests.
When determining the above-mentioned evaluation items, mechanical and electrical parameters are established for the head testing device. The following are the mechanical parameters: The radius, which is represented by distance when the center of the disk is the reference point; the skew angle, which is the angle formed between the head and the circumferential tangent of the magnetic disk; spindle rotational speed, etc., all of which are absolute positions of the magnetic disk. The following are the electric parameters: The signal frequency, the signal current, the data pattern, the MR head bias current, etc., when magnetic signals are being written or read.
Head testing device 10 determines the above-mentioned evaluation items while simulating operation of the hard disk. For instance, the head is moved by the rotary actuator while describing an arc above the magnetic disk, as previously mentioned, and therefore, the head skew angle increases as the head moves from the side of the inner periphery to the outer periphery. The skew angle relative to the radius varies with each type of HDD, even if the radius remains the same. Therefore, head testing device 10 calculates the position on magnetic disk 40 that satisfies both the radius and the skew angle and positions the head at the position obtained by calculation. Head 20 moves in micro-increments within the track above the magnetic disk while moving between tracks in order to determine fluctuations in the determination results when head 20 is being tested, for instance, during track profile determinations. The testing time for head 20 includes movement such as movement within a track and movement between tracks, etc., and therefore, it is preferred that head 20 linearly move the shortest distance so that the movement time for head 20 will be curtailed in order to reduce the testing time of head 20. Nevertheless, when head 20 moves linearly above magnetic disk 40, there is a chance that head 20 or cassette 30 holding head 20 will impact spindle 51 holding magnetic disk 40, etc.
A specific example of impact is shown in FIG. 2. FIG. 2 is a diagram of head 20 attached to cassette 30 and magnetic disk 40 held by spindle 51, seen from above. The skew angle of head 20 is 0 degrees directly beneath with spindle 51 in the center, that is, when head 20 is at 3 o""clock, but when the head moves toward 2 o""clock, the skew angle becomes xe2x88x9230 degrees, and when the head moves toward 4 o""clock, the skew angle becomes +30 degrees. It is therefore clear that when head 20 moves from the standby position away from magnetic disk 40 to a predetermined position above magnetic disk 40 in FIG. 2, cassette 30 impacts spindle 51 if head 20 moves linearly. Moreover, when the movement of head 20 is confined to a fixed path in this same way so that it will make a wide circle around spindle 51 in order to automatically avoid impact, head 20 does not stay above magnetic disk 40 and this poses a problem when head 20 is floating above the magnetic disk. Therefore, by means of the prior art, a path of movement for head 20, cassette 30, spindle 51, magnetic disk 40, etc., of head testing device 10 when head 20 is moving is pre-selected so that head 20 can avoid impact from other objects when head 20 is moving, and this path is based on the shape data of head 20, and objects surrounding head 20, and head 20 is moved in accordance with this selected path.
Nevertheless, there is a problem in that the time necessary for the impact-avoidance operation imposes on the head testing time. Head movement includes movement in micro-increments within a track, movement between tracts, and further, movement inside and outside the magnetic disk region. There is no impact of the head and cassette with other objects during movement in micro-increments within a track, and there is also no impact when the head slips from above the magnetic disk. There have been no problems with the strict impact avoidance operation for all movements in the past because magnetic information is read and written in track units and determinations are conducted once while the magnetic disk rotates once. Nevertheless, today""s tracks are further subdivided and determinations are conducted in head tests based on reading and writing of magnetic information in sector units and it is necessary to wait for the head movement to be completed for each determination. There is a strong demand for HDDs, beginning with computers, but cost competition is intense and there is a desire to reduce testing time in order to reduce manufacturing costs. Therefore, there is a need for a head-positioning control method for curtailing the head movement time, which is one element of the testing time.
The object of the present invention is to solve the above-mentioned problems of the prior art, its purpose being to judge whether or not an impact avoidance path is necessary in accordance with the head movement distance and thereby move the head on a fixed path without performing the operation of the impact avoidance path and thus improve the speed of the head positioning.
Another object is to present a testing device with which either one or both of the head and recording medium to which a spin stand for head determination is attached is or are tested, and with which high-speed, as well as high-precision determination is possible using a method for improving head-positioning speed.
In short, the first invention is one wherein by means of the method for head positioning of a device having a recording medium, a head for operating the recording medium and sending and receiving information to and from this recording medium, and a positioning control mechanism that positions by moving the head from the first to the second position in accordance with position commands, the above-mentioned position commands are received and it is determined whether or not the distance between the above-mentioned first position and the above-mentioned second position exceeds the predetermined threshold and if the above-mentioned distance does not exceed the above-mentioned predetermined threshold, the above-mentioned head is moved along a predetermined fixed path, while if the above-mentioned distance exceeds the above-mentioned predetermined threshold value, one of several possible paths is selected and the above-mentioned head is moved along the above-mentioned selected possible path.
Moreover, the second invention is one wherein by means of the method for head positioning of a device having a recording medium, a head for operating the recording medium and sending and receiving information to and from this recording medium, and a positioning control mechanism that aligns by moving the head from the first to the second position in accordance with position commands, the above-mentioned position commands and path selection approval commands that approve the operation of path selection are received, and if the above-mentioned path selection approval commands do not approve the path selection, the above-mentioned head is moved along the predetermined fixed path based on the above-mentioned position commands, while if the above-mentioned path selection approval commands do approve the path selection, one of several possible paths is selected based on the above-mentioned position commands and the above-mentioned head is moved along the above-mentioned selected possible path.